DHW thermostat stops heating

Hi. I have a problem in my new house. It's a 'standard' gas boile

feeding the heating and a DHW tank. There's a 3-way solenoid valve o the exit from boiler to control flow to DHW, CH or both. There was a DHW tank thermostat fitted but missing the cable. The inpu for the thermo, in the controller panel, had been bypassed so that DH is heated to the same temp as CH water, ie too hot for me. The problem is that, when I wired the DHW thermo back in, when i reaches the set temp the hot water cuts off as expected but so does th CH. Is this down to the way the programmer and controller panel have bee installed? The panel has a number of wires around the edge, some o which have been clipped. I assume they are left intact/clipped t select various options during installation. I don't have instruction to decipher though. Thanks

-- jashton

Reply to
jashton
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More likely, a 3-port mid-position motorised valve.

You have a wiring problem. Your system needs to be wired as per the Y-Plan diagram in

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(with the possible exception that the pump may need to be controlled by the boiler rather than being wired exactly like the diagram).

The important thing is that the cylinder stat *must* have 3 contacts - and be of the change-over variety - and all 3 wires must be connected. When the HW is hot, the stat *must* provide a HW-satisifed signal, which must be connected to the 3-port valve's grey wire. The valve needs to turn the boiler on when only CH is required, and cannot do so unless its grey wire is powered.

There should also be a HW-off connection to the programmer. If this is connected correctly, you may find that the CH works when you turn HW off at the programmer. This may offer a short-term solution while you sort out the stat wiring.

Reply to
Set Square

Note that the boiler cuts out for a delay of a few seconds or so after the DHW thermostat has satisfied until the 3-port valve has gone all the way to CH only.

It is always better to wire the controls understanding how they work than to use some sort of "simplified" wiring centre which supposedly makes the task easier.

Reply to
Ed Sirett

Oh good, they've put it right again! Anyone notice that Honeywell had re- (or rather dis)-organised their web site about a week ago so that their own links went to 404s and Directory Listing Denied-s all over the place?

Reply to
John Stumbles

Or better still, both: I like the Drayton wiring centres (only about sick squid from bee and queue) since you can see what the links do (unlike the honeywell PCB types) but they make it fairly idiot proof, both for you when you're wiring it all up at the end of a long day/week and your brain's already clocked off, and for whoever comes after you. Don't you hate trying to debug a mass of spaghetti crammed into a single socket box? :-)

Reply to
John Stumbles

Yes, I remarked on it at the time - but checked that it had been restored before quoting the link in this thread.

Reply to
Set Square

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